The present invention relates, in general, to testing semiconductor devices and, more particularly to measuring variations in propagation times, or delays, through semiconductor devices with the use of ratiometric time measurements.
A crucial step in the manufacture of semiconductor devices is the testing of those circuits. A continuing problem in the area of testing semiconductor devices is that as the circuits in the semiconductor devices become faster, testers employing older slower devices cannot operate fast enough to perform the tests. This problem is severely compounded when the measurement being taken is that of the variances in propagation times among a production lot of semiconductor devices.
Accordingly, it is an object of the present invention to provide an apparatus and method for testing semiconductor devices which overcomes the above deficiencies.
A further object of the present invention is to provide an apparatus and method for testing semiconductor devices which is capable of measuring picosecond, or less, differences in propagation delays of semiconductor devices.
Another object of the present invention is to provide an apparatus and method for testing semiconductor devices which is accurate.
Still another object of the present invention is to provide an apparatus and method for testing semiconductor devices which does not require full scale calibration.